Intentional or unintentional microwave or radio frequency (RF) interference may be coupled through I/O pins or antennae in sealed packaged chips. This interference may affect the operating point, the gain, input and output impedances of devices and various circuit elements. The result of microwave or RF interference depends on the received signal strength and characteristics, for example, pulse width/height, and may range from temporary performance modifications to permanent damage of the effected device. Effects of the microwave or RF interference onto the devices and circuit elements are difficult to monitor and predict, and therefore, protection of the devices and circuits from unwanted interferences is a long-standing problem which needs to be resolved.
Various developments have been made for prevention from interference in receiving signals. For example, U.S. Pat. No. 6,169,888 is directed to a receiving antenna scanning diversity system with controllable switching in which provision is made to eliminate interference in receiving signals. In this device, the interference detector is located within the receiver to generate and to transmit an indication signal, or a signal derived therefrom. Such signal may be converted into a switching signal that affects the switching condition in the antenna installation having the controllable switching circuit.
There are known on-chip interference protection devices for integrated circuits and other electronic components and equipment. For example, the Patent Application Publication 2002/0047728 is directed to an integrated circuit having integrated within it an RF filter device which can prevent or restrict the propagation of high frequency interference signals through lines carrying DC voltages or low frequency voltages required for the operation of the integrated circuit.
In U.S. Patent Application Publication 2002/0030471, an on-chip filter regulator acts as a voltage regulator and a low pass filter. The voltage regulator generates a constant DC output voltage and relays the DC voltage against instantaneous load changes. The low pass filter actively filters the interference out of the DC output voltage.
U.S. Pat. No. 6,243,247 is directed to a strip line transient protection device for protection from radio frequency and microwave frequency interference. The transient protection device has three ports: surge port, a protected port, and a ground port. The surge port receives and/or transmits transmission signals from and to transmission lines and receives a surge or electrical energy from transmission line. The ground port dissipates or discharges the surge or electrical energy to a system ground. The protected port receives and/or transmits transmission signals from and to the circuit board. The transient protection device is the first component in the circuit board that the surge reaches. The surge does not reach the protected port since the transient protection device acts as a capacitor to attenuate or block the surge.
U.S. Pat. Nos. 5,241,697; 5,339,463; and 5,369,470 are all directed to receivers which have circuitry for changing the signal transmission characteristics in response to receiving an interference signal. The protection circuitry includes a detector module with detector circuits for detecting value characteristics of receiving or interference states. The circuitry for changing the signal transmission characteristics also includes an evaluation circuit having at least one amplitude and/or time threshold circuit connected with its detector module and further includes a logic unit which provides processed signals characteristic of received and interference states as control signals. One of the detector circuits in the detector module determines if the signal exceeds a predetermined value, and if such determination is made, the signal characteristics are changed.
Despite a number of developments made by engineers and scientists in the art of protection from microwave and radio frequency interference, the present interference protection system and a method for protecting a device from an interference signal is a further development advance where the specific combination of elements have not been previously attained.